Modular gating system for foundries

ABSTRACT

The present invention of a gating system comprises the use of modular gating system consisting of one or more filtering media flanked on at least one side by an evaporative foam layer, which is left inside the mold. The modular gating system permits the entry of metal to any surface of the mold without going through the parting line of the pattern.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application is entitled to the benefit of Provisional Patent Application No. 60/473,778 filed on May 27, 2003 by Edgardo Campomanes titled “Modular Gating Systems for Foundries”

BACKGROUND: FIELD OF INVENTION

[0002] This invention relates to the use of a modular gating system to conduct molten metal from the pouring basin of a mold to the main cavity of the mold containing the actual casting impression.

BACKGROUND—DESCRIPTION OF PRIOR ART

[0003] A description of a conventional gating system normally employed in foundries is shown in FIG. 1. The conventional configuration of any pattern provides a draft angle so that the pattern can be drawn from the parting line or from the surface of the mold. Any projections wider than the angle draft will result in an undercut, which would prevent the pattern from being withdrawn and would therefore, destroy the mold. Because of this requirement, the elements of the gating system including the filtering media are usually placed on the parting line of the mold. This arrangement, therefore, requires the metal to travel from the pouring basin, into the down sprue, to the part line where filter is usually placed, and into the mold cavity. In doing so, the yield of the casting process is lower since the metal has to fill all the elements of the gating system. Furthermore, because of this longer distances traveled by the metal, more temperature is lost before the metal enters into the main casting cavity. This could cause a problem in the manufacture of thin castings.

SUMMARY

[0004] In accordance with the present invention a gating system comprises the use of modular gating system, which contains a filtering media flanked on at least one side by an evaporative foam layer made of expanded polystyrene, which is left inside the mold. The modular gating system permits the entry of metal to any surface of the mold without going through the parting line of the pattern. The term modular gating system is used to denote that the gating system is not an integral part of the pattern and that it is an independent module that can be used with other patterns.

Objects and Advantages

[0005] Accordingly, several objects and advantages of the present inventions are:

[0006] 1. To provide a gating system that can be placed on any area on the cope side (Upper part of the mold) of the mold without going through the part line.

[0007] 2. To provide a gating system that is compact and eliminates the need to go to the part line thus increasing yield and minimize heat loss.

[0008] 3. To provide a gating system that eliminates chances of slag by-pass, which happens when the parting line of the mold is warped as shown in FIG. 7.

[0009] 4. To provide a means of feeding the casting by gating directly into isolated thermal centers thus eliminating the need for a riser.

DRAWING FIGURES

[0010]FIG. 1 is a mold showing where cross sectional views are taken.

[0011]FIG. 2 is a cross sectional view of a normal mold showing the essential parts of the gating system.

[0012]FIG. 3 is the same cross sectional view of the same mold using modular gating system.

[0013]FIG. 4 shows the isometric view of a modular gating system

[0014]FIG. 5 shows a variation where the upper evaporative foam is eliminated. Pouring basin sit on top directly on the filter.

[0015]FIG. 6 shows the filter of the modular gating system placed directly on top of the casting.

[0016]FIG. 7 shows multiple filtrations where 2 filters are used in series.

[0017]FIG. 8a and 8 b show the foams height is considerably increased in order to function as a riser

[0018]FIG. 9 shows some slag by-pass caused by a warped mold

Reference Numerals in Drawings:

[0019]10 Pouring Basin

[0020]14 Down-sprue

[0021]16 Upper Evaporative Foam

[0022]18 Filter

[0023]20 Lower Evaporative Foam

[0024]22 Ingate

DESCRIPTION—FIG. 3 and 4—Preferred Embodiment

[0025] A preferred embodiment of the modular gating system is illustrated in FIGS. 3 and 4. The gating system consists of a pouring basin (10), a downsprue (14), a slab of evaporative foam (16) covering a slightly smaller in area than the filtering media and resting on top of the filter (18). Another slab of evaporative foam is glued at the bottom of the filter with an area slightly smaller than the filter (20). The thickness of the foam is such that it would reserve enough volume for the metal to displace in order to prevent freeze up from occurring when the metal passes through the tiny holes of the filter. The foam is connected to the casting through an ingate (22).

[0026] Typically, the area covered by the evaporative foam is slightly smaller than the live area of the filter. A ledge of reasonable width is left around the foam as this serves as an anchor to hold the filter in place once the foam is replaced by the metal. The size of this ledge is proportional to the size of the filter but it must be strong enough to hold the filter in place while the metal passes through. This arrangement is shown in FIG. 4. The recommended dimension of the filter is given by filter manufacturers.

FIGS. 5, 6, 7 and 8—Alternative Embodiments

[0027] Alternative embodiments are shown in FIGS. 5, 6, 7 and 8. In FIG. 5, the pouring basin is placed directly on the filter. The Down-sprue and the upper foam are eliminated. The draft angle of the pouring basin is towards the surface so that it could be withdrawn from the top.

[0028]FIG. 6 shows the lower foam eliminated and filter is placed directly on the casting. The angle of draft of the casting is towards the parting line so that it can be withdrawn together with the rest of the pattern.

[0029]FIG. 7 shows the modular system using multiple filters. In this example, 2 filters are used series. The filters may have different filtering characteristics. Examples: . coarse filtration, followed by fine filration, or one filter has a greater affinity for sulfides the next for oxides. The number of filters placed in series is not limited to two. FIG. 8a and 8 b shows the foams height is considerably increased in order to function as a riser.

Advantages

[0030] From the above description, a number of advantages become evident with the use of this system:

[0031] Because it provides a gating system that can be placed on any area on the cope side (Upper part of the mold) of the mold without going through the part line, the weight of modular gating system is considerably lighter thus the yield is increased,

[0032] Because it provides a gating system that can be directly placed on top of isolated thermal centers, it may eliminate the need for risers.

[0033] Because of the distance traveled by the metal is less, heat loss is minimized which is critical in casting thin sections and rangy castings.

[0034] Because the uncovered area of filter is completely encased in sand, chances of slag by-pass are eliminated. The diagram in FIG. 9 shows how slag by-pass can occur when filter is placed on the parting line

[0035] Because of the possibility of using multiple filters in series, a cleaner casting can be obtained.

Operation

[0036] The pattern is prepared for molding. The foam filter, down sprue and pouring basin assembly is placed on top of an ingate and is temporarily held in position by the molder while the sand is being introduced. The use of pins or dowels is recommended to prevent the assembly from wandering when the sand is being introduced. The pattern is then withdrawn, from the bottom of the mold. The pouring basin and down sprue is withdrawn from the top. The foam is left in the mold. The mold is now ready to accept metal.

Conclusion, Ramification and Scope

[0037] Accordingly, the reader will see that the modular gating system can be used effectively while considerable benefits can also be derived from its usage. The modular gating system consists of an assembly of pouring basin, downsprue and filtering media flank on both side and one side with foam and an ingate. Metal enters through the basin, into the downsprue and displaces the volume of the foam before and after the filter(s). It flows through the ingate and into the main casting cavity.

[0038] Several benefits come with this process.

[0039] Less metal is needed to fill up the mold because of the shorter travel required for the metal to enter the main casting cavity.

[0040] This process also makes it easier for feeding castings with thin sections as heat loss through the walls of the gating system is reduced since the area to which the metal is in contact is less before it enters the casting cavity.

[0041] Since there are no gaps between the filter edge of the filter and the sand, slag by-pass is virtually eliminated. This is a common occurrence when the filter is set on parting line. This is illustrated in FIG. 8.

[0042] Because of the accessibility of the top surface of the casting to be fed first, a riser used to feed isolated thermal center can be eliminated as in FIG. 8a and 8 b.

[0043] The use of multiple filters in series can result in cleaner metal. 

1. I claim a modular gating system which contains a filtering media flank on one side or both sides by an evaporative foam pattern.
 2. I claim a means of anchoring a filtering media in the sand by providing a ledge defined by the sand and the outside shape of the evaporative foam pattern.
 3. I claim a means of risering the casting by placing the above-described modular gating system on top of the portion of the casting that needs feeding.
 4. I claim a means of filtration of metal using two or more filters placed in series each separated by an evaporative foam pattern and used in conjunction with the above described modular gating system. 